Year: 2014
Type: article
Abstract: Recent CLAS data for the |$\pi \Sigma $|-invariant mass distributions (line-shapes) in the |$\gamma p \to K^{+} \pi \Sigma $| reaction are theoretically investigated. The line-shapes have peaks associated with the |$\Lambda (1405)$| excitation. Our model consists of gauge-invariant photoproduction mechanisms, and the chiral unitary model that gives the rescattering amplitudes where |$\Lambda (1405)$| is contained. It is found that, while the |$\pi \Sigma $| line-shape data in the |$\Lambda (1405)$| region are successfully reproduced by our model for all the charge states, the production mechanism is not so simple that we need to introduce parameters associated with short-range dynamics to fit the data. Our detailed analysis suggests that the nonresonant background contribution is not negligible, and its sizable effect shifts the |$\Lambda (1405)$| peak position by several MeV. We also analyze the data using a Breit–Wigner amplitude instead of those from the chiral unitary model. We find that the fitted Breit–Wigner parameters are closer to the higher pole position for |$\Lambda (1405)$| of the chiral unitary model. This work sets a starting point for a fuller analysis in which line-shape as well as |$K^+$| angular distribution data are simultaneously analyzed to extract |$\Lambda (1405)$| pole(s).
DOI: 10.1093/ptep/ptt121
Authors: S. X. Nakamura, D. Jido
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $979
OpenAlex ID: W2102092862